#include<iostream>
using namespace std;
class Circle {
private:
    double radius;
public:
    Circle(double r) : radius(r) {}
    friend double calculateArea(Circle c);
};

double calculateArea(Circle c) {
    return 3.14 * c.radius * c.radius;
}
int main() {
    Circle circle(5);
    std::cout << "Area: " << calculateArea(circle) << std::endl;
    return 0;
}